Its common for people to think that C# is a Java rip off, mainly because they dont know the history of C#. Java is actually a Delphi rip off, and a really bad one and the same guy that made Delphi for Borland went to Microsoft to create C#. Delphi is a rip off of Smalltalk. Smalltalk is a rip off of Lisp. Lisp is a rip off of lambda calculus … and the rabbit hole never ends. Of course each rip off has its own special things.
So even though Microsoft did create C# as an answer to Java, library wise, C# is extremely close to the structure of Delphi and much of Delphi’s ideology which is just brilliantly designed on GUI, OOP and library level. Java on the other hand is a huge pile of mess on all these three departments.
If one can integrate C# into Unreal what stops you from integrating Java ?
Frankly I dont see the point. C# , Java , Javascript , whatsover never will come remotely close to the productivity , ease of use and flexibility of Blueprints. Python , Lua , Ruby are the ones that can really be useful to indie developers and small studios.